docs: flat UDP spec -- drop time_mode, record the batching and event rules found in acquisition.cpp

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/superpowers/specs/2026-11-02-flat-udp-source-design.md

@@ -24,7 +24,7 @@ Read from `UDPSender::Synchronise()` and `MemoryDataSourceI`:
 
 | Question | Decision |
 | --- | --- |
-| Time base | Both. `time_mode=rate` (default): the user declares the cycle rate in Hz; frames are spaced `1/rate` and no loss is ever reported. `time_mode=arrival`: each datagram is stamped with its receive time. |
+| Time base | The user declares the nominal cycle rate in Hz (`rate`, required). The existing pipeline stamps the frames: anchored at arrival, samples spaced by the declared cadence, corrected to the measured cadence when the arrivals are more than 25% off it; `--relative-time` gives a purely counted clock. There is no `time_mode` switch: `acquisition.cpp` has no stamping path that ignores the declared cadence, and `sampling_rate = 0` would size the ring and the ingest decimation for 1 kHz (`model.cpp:60`). Loss is never reported (`lost = 0`). |
 | Signal list entry | A row editor: name entry, type dropdown, element count and a remove button per row, plus an "Add signal" row. |
 | Network | Port and optional bind address, plus an optional multicast group and interface. No source-address filter. |
 | Byte order | `little` (default) or `big`. |
@@ -40,8 +40,7 @@ Persisted in the session, settable with `--source-opt`. Kind id: `flatudp`.
 | `bind` | empty | Local address to bind; empty is any. |
 | `multicast` | empty | Group to join; empty is plain unicast. |
 | `iface` | empty | Local interface address for the join. |
-| `rate` | none | Cycle rate in Hz. Required when `time_mode=rate`. |
+| `rate` | none | Nominal cycle rate in Hz. Required; sizes the ring and the decimation and spaces samples within a frame. |
-| `time_mode` | `rate` | `rate` or `arrival`. |
 | `endian` | `little` | `little` or `big`. |
 | `signals` | none | `name:type[count],...`, e.g. `Trigger:uint8,Ia:float32,Wave:float32[16]`. A persistence format only: the form builds and parses it. |
 
@@ -49,7 +48,7 @@ Types: `uint8/16/32/64`, `int8/16/32/64`, `float32`, `float64`. Count 1 is a sca
 is a vector signal. Expected datagram size is the sum of `size * count` over the rows.
 
 Validity (form and `--source-opt` alike): at least one signal; names non-empty and unique;
-count 1-4096; total size at most 65507 bytes; `rate > 0` when `time_mode=rate`.
+count 1-4096; total size at most 65507 bytes; `rate` finite and positive.
 
 ## Architecture
 
@@ -68,26 +67,26 @@ Threading is unchanged: the source lives on the producer thread and `poll()` doe
 `poll(timeout_ms)` waits on a non-blocking UDP socket and drains it.
 
 - A datagram of exactly the expected size is decoded row by row to doubles (byte-swapped when
-  `endian=big`) and delivered as one `Frame`: `num_samples = 1`, `counter` a running count,
+  `endian=big`).
-  `lost = 0`, `late = false`, `recv_time` the arrival clock.
+- **Batching.** When every row is scalar, decoded datagrams are queued and delivered
-- `set_datagram_tap` is honoured and `has_datagrams()` is true, so packet capture works.
+  `block` at a time in one `Frame` (`num_samples = block`), where
-- `on_config` is called once on open with one `SignalInfo` per row (`rows = count`,
+  `block = clamp(round(rate / 100), 1, 1024)`, about 100 frames per second as the E-1608 does. A
-  `cols = 1`).
+  partial block is flushed after 100 ms so a slow or stopped sender does not hold samples back.
-
+  When any row is a vector, a vector signal carries one sample per `Frame`, so each datagram is
-### Time
+  its own frame (`num_samples = 1`).
-
+- `Frame`: `counter` a running frame count, `lost = 0`, `late = false`, `recv_time` the arrival
-- `rate`: every signal has `time_mode = kTimePacket` and `sampling_rate = rate`, as the E-1608
+  clock at delivery.
-  does. Spacing comes from the declared rate; jitter does not appear in the trace.
+- `set_datagram_tap` is honoured for every datagram, valid or not, and `has_datagrams()` is
-- `arrival`: `sampling_rate = 0`, so the existing arrival-clock path stamps each frame.
+  true, so packet capture works.
-- **To confirm in the plan:** that `acquisition.cpp`'s packet path with `sampling_rate = 0`
+- `on_config` is called from the first `poll()` with one `SignalInfo` per row (`rows = count`,
-  really stamps on arrival and does not degenerate. If it does not, the plan adds the small
+  `cols = 1`, `time_mode = kTimePacket`, `sampling_rate = rate`).
-  change there.
 
 ### Errors and state
 
 - A wrong-size datagram is dropped, never decoded. Each distinct size raises one `Error`
   event ("datagram of N bytes, expected M, check the signal list") and increments `stale`.
-- `connected` becomes true after the first valid datagram and false after 2 s of silence.
+- `Connected` is raised on the first valid datagram and `Disconnected` after 2 s of silence; a
+  later datagram raises `Connected` again.
 - A bind or multicast-join failure raises an `Error` and the source stays disconnected.
 
 ### Connect form
@@ -95,8 +94,7 @@ Threading is unchanged: the source lives on the producer thread and `poll()` doe
 Built from `AdwPreferencesRow`s, with the destroy-notify guard used by the E-1608 form.
 
 - Network group: port, bind, multicast, interface.
-- Timing group: rate spin and time-mode combo. The rate spin is **disabled, not hidden**, in
+- Timing: a rate spin.
-  arrival mode.
 - Byte order combo.
 - Signals group: one row per signal, "Add signal" at the bottom, and a live subtitle with the
   implied size ("41 bytes per datagram"). `valid()` is false while the list breaks a validity
@@ -110,7 +108,7 @@ No unit suite; the self-check is the contract.
 - `tools/mock_flatudp.py`: emits packed structs for a given signal spec and rate; options for
   big-endian and for one wrong-size datagram.
 - `UDPSCOPE_PROBE_FLATUDP` in `src/ui_probe.cpp`: stream names and count; a hand-computed
-  decode of known values including a vector signal and a `uint64`; rate-mode spacing; the
+  decode of known values including a vector signal and a `uint64`; the declared rate reaching the model; the
   wrong-size error reported once and counted in `stale`; disconnect after silence; the form's
   validity rules; the `signals` codec round trip. A multicast loopback check runs if the
   sandbox allows it.